The 3G and 4G have higher and higher requirements for rate and burst of high speed data service, and the most important feature of the high speed data service is the burstiness.
The Hybrid Automatic Repeat Request (HARQ) technique is one of error control techniques, and with the development of the wireless services, the HARQ plays a more and more important role in the wireless communication field. There are reasons in mainly two aspects: first, most wireless services in the future are uplink and downlink, asymmetry and burst packet data services, which don't have a high requirement for delay, but have a very high requirement for data quality in transmission. Second, the wireless propagation environment is especially complex, and the received signal not only has various fading and the Doppler shift caused by moving, but also is affected by various interferences and noises. These fading and interferences easily cause random errors and burst errors, which will severely affect the transmission quality. Combining the Forward Error Correction (FEC) and error detection plus Automatic Repeat Request (ARQ) forms the HARQ. Each sent data packet includes check bits of the error correction and error detection. If the number of error bits in the received packet is in the error correcting capability, the errors will be corrected automatically; when the errors are severe, and beyond the error correcting capability of the FEC, the sending end should retransmit. This mode reduces the decoding complexity of the FEC mode to a certain extent, and avoids the drawback of the bad information transmission coherence of the ARQ mode. Briefly, the HARQ can improve the system performance greatly, and flexibly adjust the rate of valid code element, and also solve the bit error problem caused by adopting the link adaptation, and be suitable for applying in the transmission of large data packets.
There are currently many methods for accessing a reverse common channel in the wireless network, such as the random ALOHA access mode, the slot ALOHA mode, and so on, and at present, these methods are more suitable for sending shorter burst data.
For the access requirement of the reverse common channel in wireless high speed data network, not only higher and higher burst data should be carried, for example some burst data with large amount of data (such as pictures, multimedia burst short messages and so on), but also transmission is carried out in the common channel in the burst ways as much as possible, and the dedicated channel is not used to carry out the transmission as much as possible to save the resources of the reverse dedicated channel and reduce the transmission delay of the burst data. However most of the current methods which are put forward for accessing the reverse common channel are unable to carry multiple users random high speed burst data, and reverse performance of the network is affected greatly, and more interference is caused, for example, in the Do Rev. A system, the maximum rate of reverse burst data is only 38.4 kbps.